1. Field of the Invention
The present invention relates to a charged particle beam writing method, a readable storage medium and a charged particle beam writing apparatus, and more particularly to a technique for obtaining an amount of an irradiation of an electron beam to enhance a line width uniformity in electron beam writing.
2. Related Art
A lithographic technique for progressing a microfabrication of a semiconductor device is only one of very important processes for generating a pattern in a semiconductor manufacturing process. In recent years, circuit line widths required for the semiconductor devices have been reduced every year with an increase in an integration of an LSI. In order to form desirable circuit patterns on these semiconductor devices, an original picture pattern (which will also be referred to as a reticle or a mask) with high precision is required. The electron beam writing technique has an originally excellent developing property, and is used for producing the original picture pattern with high precision.
FIG. 25 is a conceptual view for explaining an operation of a conventional variable-shaped electron beam writing apparatus.
A rectangle, for example, oblong opening 411 for forming an electron beam 330 is provided on a first aperture 410 in a variable-shaped electron beam writing apparatus (EB (Electron Beam) writing apparatus). Moreover, a variable-shaped opening 421 for forming the electron beam 330 transmitted through the opening 411 of the first aperture 410 to have a desirable rectangular shape is provided on a second aperture 420. The electron beam 330 irradiated from a charged particle source 430 and transmitted through the opening 411 of the first aperture 410 is deflected by means of a deflector, and is transmitted through a part of the variable-shaped opening 421 of the second aperture 420 and is thus irradiated on a target workpiece 340 mounted on a stage to be continuously moved in a predetermined direction (which is assumed to be an X direction, for example). More specifically, the rectangular shape in which the electron beam 330 can be transmitted through both of the opening 411 of the first aperture 410 and the variable forming opening 421 of the second aperture 420 is drawn in a writing region of the target workpiece 340 mounted on the stage to be continuously moved in the X direction. A method of transmitting the electron beam 330 through both of the opening 411 of the first aperture 410 and the variable forming opening 421 of the second aperture 420, thereby creating an optional form is referred to as a variable-shaped method.
In recent years, there has been a chemical amplification type resist as one of resists used often for an electron beam exposure. The chemical amplification type resist has a problem in that an optimum amount of an exposed dose is changed by leaving before and after the exposure. As a technique for solving the problem, a change in a resist sensitivity is determined by measuring a film thickness and the like of a corrected exposure pattern. A technique for carrying out an irradiation through a blurred beam having a beam diameter of approximately 20 μm again has been disclosed (see JP-A-2000-267259, for example).
As described above, the chemical amplification type resist has a problem in that the optimum amount of the exposed dose is changed by leaving before and after the exposure. In other words, in the case in which the chemical amplification type resist is used for manufacturing a mask, a line width dimension (CD) obtained after the writing of the mask to be a workpiece fluctuates (PED).
In the technique described in JP-A-2000-267259, there is a problem in that a correction with high precision cannot be carried out because a dose error for each pattern category is made. Moreover, there is a problem in that a pattern for determining an amount of a corrected exposure is necessary and a film thickness measuring device and an exposure auxiliary chamber are required in addition to an exposing apparatus body.
It can be supposed that the fluctuation (PED) in the line width dimension (CD) obtained after the writing of the mask is caused by a diffusion of acid generated by the writing. The diffusion of the acid is caused in a region of several tens nm and has a rate of approximately of 1.0 nm/h. On the other hand, in the electron beam writing, it has been known that the CD error for each pattern depending on an area density is made by a proximity effect (a range of several tens μm). It is necessary to change and correct an exposure dose or “irradiation amount” for each area density in order to correct the proximity effect, and a base dose and a proximity effect correction coefficient η are used. There can also be proposed a technique for predicting the CD error of a pattern based on a time and writing pattern data obtained by previously resizing pattern data, thereby correcting the fluctuation (PED) of the line width dimension (CD) obtained after the writing of the mask in the case in which a writing order for a pattern or a chip to be written on the workpiece can be controlled. However, there is a problem in that a very long time is required for resizing the pattern and a date volume is also increased.